The weakest and roughest portion of a sheet of paper coming off the Fourdrinier paper-making machine has always been the extreme lateral edges of the sheet (a strip approximately 12" to 24" wide). Frequently, this strip is so poor in quality that they must be diverted to cheaper grades or culled completely. Many devices have been tried to improve the overall profile and quality of the sheet, but in general, the edges do not improve in quality along with improvements to the rest of the sheet. There is no known device that is exclusively directed to improving the edge of the sheet. The rotating device of the present invention will provide a tool to bring the quality of the edges of the sheet closer to the quality of the rest of the sheet. Not only will this improve the quality and strength of the sheet edge, it will greatly improve the runability of the sheet through the paper machine, thus resulting in less down time.
The Fourdrinier paper-making process involves a traveling endless screen or forming fabric onto which is fed an aqueous dispersion or slurry of fibers of cellulose or other materials. This aqueous dispersion is fed onto the fabric from a headbox at a rate or velocity substantially equal to the speed of the fabric (plus or minus 20%). While this aqueous slurry is in its most liquid state before the dewatering devices begin removing the water, the slurry will tend to run to and off the sides of the moving forming fabric. This invention will curl or lift the edge of the fabric to stop this flow over the edges.
There have been several attempts to solve this problem; many are in use today but all have serious drawbacks. The devices in use today are all stationary "curlers" made from plastic materials. Typical of such is U.S. Pat. No. 3,928,124 to Hansen. Although these devices do curl the edge of the fabric, their stationary design causes friction on the moving fabric and causes serious edge wear and considerably shortens the life of the forming fabric. Papermakes have a real need to employ edge curling devices but they cannot afford to damage the expensive forming fabric. The present invention will give the papermaker a device which will curl or lift the edge of the forming fabric with a rotating tool so as to contain the slurry on the edge without damage to the fabric. With this frictionless tool, the papermaker can do things with the fabric that he would not dare do with stationary devices.
It is an object of this invention to provide a novel papermaking device to contain the slurry on the edges of the moving forming fabric. It is another object of this invention to provide a unique device to lift or change the plane of travel of the fabric and, therefore, rearrange the slurry and improve the edge of the sheet on the Fourdrinier forming fabric. Still other objects will become apparent from the more detailed description which follows.